Mobile Cellular and Personal Communication Service (PCS) devices typically provide for transmission and reception of signals through one of two antenna configuration options. One option is to transmit and receive through an internal antenna, permanently attached to the device itself, and provided so that the device always remains portable and mobile. The second option is to use an external antenna, often a car mounted antenna and usually connected via an accessory transmission cable from an adapter on the device to a connector configured to deliver and receive transmissions over the external antenna. Selection between the two antennas is accomplished utilizing a switch. Implementation of an antenna selection and porting switch in practice mandates a low loss switch implementation, thereby minimizing the degradation of received signal strength and preserving transmitted power.
Additionally, most mobile handsets position the internal antenna port, and consequently the internal antenna, at the top portion of the handset, while placing the external antenna port at the bottom of the handset. Such a configuration, although ergonomically convenient for the end user, mandates the incorporation of an internal radio frequency (RF) transmission medium from the top end of the handset to the bottom end. The RF signal transmission path must be selectable via the aforementioned switch. A common prior art implementation for providing a transmission path for the RF signal from switch to external antenna port is via incorporation of a low loss RF coaxial cable from the top of the handset to the bottom external antenna port. However, this method is a costly manufacturing technique.
Furthermore, the advent of allocation of a PCS communications bandwidth has motivated many communication system manufacturers and designers to investigate methods of incorporating both PCS band transmission and cellular band transmission within one communications device. Incorporating both bands within one device provides the motivation for designers to minimize replicated components in each RF band, thereby reducing the overall complexity and cost of the new dual band devices. In consideration of the above engineering and economic restrictions, use of a common switching device, which would direct either PCS or cellular communications over either the internal or external antenna, would be most advantageous. A variety of switch types, including mechanical coxial or waveguide four-way porting switches and diversity switches, are available to accomplish the task. Mechanical coaxial or waveguide four-way porting switches, however, tend to be relatively large and extremely costly. Semiconductor diversity switches are inherently less expensive to produce and offer increased reliability as compared to mechanical type switches, but diversity switches have a drawback in that a signal must pass through two junctions within a diversity switch configuration, and therefore received and transmitted signals experience the attenuation associated with passing through two semiconductor junctions.